Solid state actuators are expected to be useful in the aerospace, and space industries, as well as in certain next generation armed forces concepts.
While ferroelectric, ferromagnetic, and twinning based actuators permit relatively high energy density, each of these actuators shares a critical weakness when considering large deformation. Each of these mechanisms are essentially volume conserving and occur at constant density, limiting deformation to local shifts in crystal structure and therefore relatively small overall deformation.
Electroactive polymers including, conducting polymers and ionic based actuation such as Ionic-Polymer-Metal-Composite or IPMC, exploit a reversible electrochemical reaction to perform mechanical work. One disadvantage of these systems, however, is that they have limited stress output. Although conducting polymers yield relatively large strain (˜1-5%), it is at low blocking stress. Macro scale conducting polymer actuators typically have stress output on the order of 1-6 MPa, and bulk energy density of 10-80 kJ/m3.
Another disadvantage is that they require a liquid or a gel electrolyte. Both the polymeric nature of these materials and the liquid electrolyte limit their applicability to a narrow temperature range. This limits the applicability of these materials to many environments commonly encountered in structural applications.